Merriam-Webster editors have produced a variety of short YouTube segments on questions of English usage (“flat adverbs”, “who” vs. “whom”, etc.) and vocabulary. (“gridiron”, “cop”, “literally”, etc.). They’re quite well done. Here’s the link:
https://www.youtube.com/playlist?list=UULGx1Xl1Nd1iJ37dWeNnp-A&feature=plcp